LONDON (Thomson Reuters Foundation) - Portugal, Moldova and Ukraine in Europe, and Laos, Cambodia and Vietnam in Asia have emerged as new child sex tourism destinations, prompting activists to call for governments to include measures to protect children in their tourism plans.

Sex tourism has spread around the world to countries that were previously inaccessible as tourism has boomed over the past 20 years and traveling has become cheaper, said a study published on Thursday by global child protection network ECPAT.

The number of international tourists almost doubled from 527 million in 1995 to 1.14 billion in 2014, it said.

In Asia, Thailand's efforts to clean up its image as a sex tourism destination and crack down on the crime, has had the unintended effect of pushing sex tourists to Laos, Vietnam and Cambodia, it said.

In Europe, Moldova, Portugal and Ukraine have emerged as new sex tourism destinations.

"Many of these countries which are starting to open up - understandably they see tourism as a fantastic economic development sector," Mark Capaldi, ECPAT's head of policy and research, told the Thomson Reuters Foundation.

He said countries looking for economic opportunities from tourism often ignore the risks that some international tourists pose to children and lack the laws to protect them. Countries need to assess the impact of tourism development projects from a child protection perspective before rushing into them, he said.

"It's much more difficult to claw back and change the reputation of a place if it becomes seen as a hotbed of child sex tourism," Capaldi said in a phone interview.

The study said a lack of data makes it difficult to assess the scale of global child sex exploitation but the crime has outpaced attempts to curb it over the past two decades.

Capaldi said the growth in online bookings and private rental accommodation have contributed to the spread of sex tourism as this has made it easier for perpetrators to remain anonymous.

The study said children from minority groups, boys and young children are far more vulnerable to sex tourism than was previously thought, as are girls and children living in poverty.

Its recommendations include creating support systems for child victims of sex exploitation in all countries, curbing the online sale of children for sex, and creating systems to enable law enforcement agencies to share information about offenders.